α-Substituted phenylacetic acid compounds, tolclofos-methyl, metalaxyl and mefenoxam are conventionally known as active ingredients of agents for controlling plant diseases (see, for example, Patent Document 1 and Non-Patent Document 1). Nevertheless, there is a continuing need for more highly active agents for controlling plant diseases.    Patent Document 1: WO 95/27,693    Non-Patent Document 1: “The Pesticide Manual—14th edition” published by BCPC, ISBN: 1901396142